Exam 1: Bacterial Nutrition and Growth Flashcards
Why do we care about bacterial nutrition?
It affects how we grow bacteria in the lab
It affects how we differentiate type of bacteria
It is the underlying fundamental reason for bacterial infection
What do all cells, including bacteria, require to grow?
A source of carbon and energy Nitrogen Phosphorus Sulfur Sodium Potassium Iron Magnesium Manganese Traces of other minerals
How do bacteria adapt to their surrounding environment?
Maximize their reproductive capability by minimizing the amount of energy they have to invest in synthesizing all the nutrients they need to live
What are the 3 major nutritional categories of bacteria?
Photosynthetic
Autotrophic
Heterotrophic
Describe photosynthetic bacteria
Can use light as the sole source of energy for growth and carbon fixation from carbon dioxide
No pathogens
Describe autotrophic bacteria
Can use inorganic molecules as the sole energy source and may use carbon dioxide or other organic molecules as a carbon source
No pathogens
Describe heterotrophic bacteria
Cannot use inorganic molecules as the sole source of energy and cannot use CO2 as the sole source of carbon
Use organic molecule as a source of carbon and energy
How are all the complex molecules require for life for heterotrophic bacteria obtained?
By either synthesis from simpler molecules or salvage from the environment
Which takes less energy, salvaging nutrients or synthesizing them?
Salvaging nutrients
What is the basic carbon source used to synthesize biomolecules?
Glucose
What can some heterotrophs grow on?
Glucose, ammonium, and phosphate ions with trace minerals
What does glucose serve as for heterotrophs?
As the energy source and the carbon source for the synthesis of nucleic acids, proteins, lipids, and carbohydrates
What do fastidious microorganisms require?
Preformed nutrients in the growth medium
Why do most bacterial species require other nutrients besides glucose?
They are missing enzymes in one or more biosynthetic pathways
What can some bacteria do when glucose is not available?
Utilize other biomolecules as energy/carbon sources by converting them into glucose
What is always going to be the preferred energy/carbon source? Why?
Glucose
It costs energy to convert other molecules into glucose
What is commonly used to taxonomically identify bacterial species?
The alternative energy sources bacteria can use that is conserved within species
What are essential nutrients required for?
Cell growth
What are the essential nutrients required by all heterotrophic bacteria?
Carbon source (glucose or an alternative if glucose is absent)
Nitrogen source
Other minerals
What are the nutrient requirements specific for each species based on?
What they are not capable of synthesizing
What do nonessential nutrients require?
Any molecules that a bacteria is capable of synthesizing, but will salvage if available
What are the types of heterotrophic bacteria?
Saprophytic
Parasitic (obligate parasites)
Both (facultative parasites)
What do saprophytic bacteria do?
Utilize dead or decaying organic material for carbon/energy sources
What do parasitic bacteria do?
Obtain nutrients directly from other living organisms
What can facultative parasites grow on?
Dead/decaying material as well as reproducing in the host and causing disease
What are most bacterial parasites classified as?
Facultative
How do facultative parasites vary in their nutrient requirements on artificial media?
Some grow on very simple media
Some are fastidious and require complex media with many nutrients due to missing biosynthetic pathways
What does it mean if a bacterial species is more fastidious?
The more adapted it is to the parasitic lifestyle
What will facultative parasites do in the host?
They will adapt and salvage the abundant nutrients available rather than synthesizing them from glucose
What can obligate parasites grow in or on?
A host. They cannot grow on artificial media
What has happened with obligate parasites since they have become so adapted to the parasitic lifestyle?
They cannot synthesize the nutrients they need to reproduce outside the host
What is the host or cell specificity of a particular obligate parasite due to?
The nutrients they require only being available in a specific host environment
What are commensal bacteria?
Cause no harm to the host of benefit the host
What are pathogenic bacteria?
Cause some harm to the host
What are opportunistic pathogens?
Bacteria that can be commensal or pathogenic, depending on the circumstance
Why is the cost of the pathogenic lifestyle high?
Because host organisms have active defense systems to avoid or kill pathogens
Why do some heterotrophic bacteria invest so much energy into adapting pathogenic mechanisms to allow them to survive in the hostile host environment?
Eukaryotic tissues are an extremely nutrient rich growth medium
What can bacteria be cultured in?
Either broth medium or on agar plates
What do agar plates allow?
The isolation of colonies that are derived from a single bacterium
What do broth cultures allow?
Growth of large batches of bacteria
What is required with broth cultures?
Shaking to oxygenate a broth culture
What are the different types of media?
Complex media Chemically defined media Differential media Selective media Enrichment media Transport media
What is complex media?
Not chemically defined
They usually contain a biological fluid or component such as blood, serum, or enzymatic digests of protein
What is chemically defined media?
Every component is known and is present at a defined concentration
What is differential media?
Some type of indicator system is added to the media (blood agar)
What is selective media?
Some type of inhibitor is added to prevent growth of certain bacteria
Selects for growth of desired bacterial species
What is enrichment media?
A liquid cultural medium that permits preferential emergence of certain bacteria that initially may have made up a relatively minute proportion of a mixed population
What is transport media?
Used for the temporary storage of specimens being transported to the lab for cultivation
Ideally maintains the viability of all organisms in the specimen without altering their concentration
Typically contain only buffers and salt
What is blood agar?
Complex differential medium
Detects hemolysis
What is MacConkey agar?
Selective differential medium
Bile salts and crystal violet inhibit gram-positive and many gram-negative species
Lactose and neutral red cause lactose fermenting colonies to turn pink
What is colistin-nalidixic acid (CAN) agar?
Selective medium for gram-positive bacteria
What is brilliant green agar?
Selective differential medium
Inhibits growth of most bacteria except salmonella
Phenol red causes colonies that do not ferment sucrose and lactose turn red
What is selenite F broth?
Used for enrichment of salmonella from feces or urine
